Automotive coating composition comprising an organosilane polymer

ABSTRACT

A coating composition containing a film-forming organosilane polymer and a sterically dispersed macromolecular polymer having hydroxy functional macromonomer arms which react with the silane functionality of the organosilane polymer. The coating compositon can be used as the clearcoat over a conventional pigmented basecoat, or as a basecoat or monocoat or primer when a suitable amount of pigment is incorporated therein. The coating composition provides improved chemical resistance and is not prone to cracking.

BACKGROUND OF THE INVENTION

This invention is directed to a coating composition useful for providinga finish on a variety of substrates. In particular, this invention isdirected to an organosilane composition which may be used for finishingautomobiles and trucks.

It is well known that consumers prefer automobiles and trucks with anexterior finish having an attractive aesthetic appearance, includinghigh gloss and excellent DOI (distinctness of image). While ever moreaesthetically attractive finishes have been obtained, deterioration ofthe finish over time, whereby the exterior finish of an automobile ortruck loses its luster or other aspects of its aesthetic appearance, maybe all the more noticeable. An increasingly observed cause of thisdeterioration is etching of the finish caused by exposure toenvironmental chemical attack. Chemicals that may cause etching of afinish include pollutants such as acid rain and chemical smog.

In order to protect and preserve the aesthetic qualities of the finishon a vehicle, it is generally known to provide a clear (unpigmented)topcoat over a colored (pigmented) basecoat, so that the basecoatremains unaffected even on prolonged exposure to the environment orweathering. It is also generally known that alkoxysilane polymers, dueto strong silane bonding when cured, exhibit excellent chemicalresistance. Exemplary of prior art patents disclosing silane polymersfor coating are U.S. Pat. No. 4,368,297; U.S. Pat. No. 4,518,726; U.S.Pat. No. 4,043,953; and Japanese Kokai 57-12058.

However, to applicants, knowledge, none of the previously disclosedalkoxysilane compositions for finishing automobiles or trucks have everbeen placed into commercial use. It is believed that heretofore known orpatented alkoxysilane coatings suffer from certain unsolved problems ordeficiencies. In particular, previously disclosed alkoxysilane coatingshave a strong tendency to cracking, which could seriously and adverselyaffect long term durability and weatherability of a finish.

There is a need for a commercially practical clearcoat finish havingexcellent appearance, including high gloss and DOI, that is alsoresistant to etching caused by chemical attack. To be commerciallypractical, such a clearcoat must not be prone to cracking. It is alsodesirable that such a clearcoat should be capable of being applied overa variety of basecoats and have excellent adhesion.

SUMMARY OF THE INVENTION

The invention is directed to a coating composition useful for finishingthe exterior of automobiles and trucks and other substrates. Thecomposition comprises:

(a) from about 20 to 90% by weight, based on the weight of the bindersolids, of a film-forming acrylosilane polymer having a weight averagemolecular weight of about 500-30,000 comprising

(i) from about 30 to 95% by weight, based on the weight of theacrylosilane polymer, of ethylenically unsaturated monomers which do notcontain a silane functionality and about 5 to 70% by weightethylenically unsaturated monomers which contain a silane functionality;and

(b) from about 10 to 60%, based on the weight of the binder solids, of adispersed polymer comprising:

(i) a core comprising a macromolecular polymer having a weight averagemolecular weight of about 50,000 to 500,000; and

(ii) attached to the macromolecular polymer, a plurality of macromonomerchains having a weight average molecular weight of about 1,000 to30,0000, comprising 5 to 30% by weight, based on the weight of themacromonomer, of polymerized ethylenically unsaturated monomers whichcomprise a hydroxy functionality; and about 70 to 95% by weight, basedon the weight of the macromonomer, of at least one other polymerizedethylenically unsaturated monomer without a hydroxy functionality; and

(c) from about 25 to 50% by weight, based on the weight of thecomposition, of a liquid organic carrier;

such that when the composition is applied as a coating to a substrate,covalent bonding between hydroxy functionalities in said dispersedpolymer and silane functionalities in said organosilane polymer reducesthe tendency of the cured coating to exhibit cracking.

The invention also includes a process for coating a substrate with theabove coating composition. The claimed invention further includes asubstrate having adhered thereto a coating according to the abovecomposition.

The composition of the present invention is especially useful forforming a clear topcoat over a pigmented basecoat. Such a clear topcoatcan be applied over a variety of colorcoats, such as water or organicsolvent based colorcoats or powder colorcoats.

DETAILED DESCRIPTION OF THE INVENTION

This invention provides a coating composition useful for finishing theexterior of automobile and truck bodies. Depending on its use, thepresent composition is capable of providing a coating which is durable,has excellent adhesion to basecoats, does not crack, does notdeteriorate in terms of transparency under prolonged exposure to weatherconditions, and imparts a superior glossy appearance for an extendedperiod. Also, the coating composition offers a significant improvementover conventionally used coating compositions in terms of resistance toetching caused by environmental chemical attack.

A typical automobile steel panel or substrate has several layers ofcoatings. The substrate is typically first coated with an inorganicrust-proofing zinc or iron phosphate layer over which is provided aprimer which can be an electrocoated primer or a repair primer. Atypical electrocoated primer comprises an epoxy polyester and variousepoxy resins. A typical repair primer comprises an alkyd resin.Optionally, a primer surfacer can be applied over the primer coating toprovide for better appearance and/or improved adhesion of the basecoatto the primer coat. A pigmented basecoat or colorcoat is next appliedover the primer surfacer. A typical basecoat comprises a pigment, whichmay include metallic flakes in the case of a metallic finish, andpolyester or acrylourethane as a film-forming binder. A clear topcoat(clearcoat) is then applied to the pigmented basecoat (colorcoat). Thecolorcoat and clearcoat are preferably deposited to have thicknesses ofabout 0.1-2.5 mils and 1.0-3.0 mils, respectively. A compositionaccording to the present invention, depending on the presence ofpigments or other conventional components, may be used as a basecoat,clearcoat, or primer. However, a particularly preferred composition isuseful as a clear topcoat to prevent environmental chemcical attack tothe entire finish. A clearcoat composition of the present invention maybe applied over a basecoat composition of the present invention.

The film-forming portion of the present coating composition, comprisingpolymeric components, is referred to as the "binder" or "binder solids"and is dissolved, emulsified or otherwise dispersed in an organicsolvent or liquid carrier. The binder solids generally include all thenormally solid polymeric non-liquid components of the composition.Generally, catalysts, pigments, and chemical additives such asstabilizers are not considered part of the binder solids. Non-bindersolids other than pigments typically do not amount to more than about 5%by weight of the composition. In this disclosure, the term binderincludes the organosilane polymer, the dispersed polymer, and all otheroptional film-forming polymers. The coating composition suitablycontains about 50-75% by weight of the binder and about 25-50% by weightof the organic solvent carrier.

The binder of the coating composition contains about 20-90%, preferably40-80%, by weight of a film-forming silane containing polymer, hereafteralso referred to as the silane polymer.

The silane polymer portion of the binder has a weight average molecularweight of about 1000-30,000, a number average molecular weight of about500-10,000. All molecular weights disclosed herein are determined by gelpermeation chromatography using a polystyrene standard.

The silane polymer is the polymerization product of about 30-95%,preferably 40-60%, by weight ethylenically unsaturated non-silanecontaining monomers and about 5-70%, preferably 40-60%, by weightethylenically unsaturated silane containing monomers, based on theweight of the organosilane polymer. Suitable ethylenically unsaturatednon-silane containing monomers are alkyl acrylates, alkyl methacrylatesand any mixtures thereof, where the alkyl groups have 1-12 carbon atoms,preferably 3-8 carbon atoms.

Suitable alkyl methacrylate monomers used to form the organosilanepolymer are methyl methacrylate, ethyl methacrylate, propylmethacrylate, butyl methacrylate, isobutyl methacrylate, pentylmethacrylate, hexyl methacrylate, octyl methacrylate, nonylmethacrylate, lauryl methacrylate and the like. Similarly, suitablealkyl acrylate momomers include methyl acrylate, ethyl acrylate, propylacrylate, butyl acrylate, isobutyl acrylate, pentyl acrylate, hexylacrylate, octyl acrylate, nonyl acrylate, lauryl acrylate and the like.Cycloaliphatic methacrylates and acrylates also can be used, forexample, such as trimethylcyclohlexyl methacrylate, trimethylcyclohexlacrylate, iso-butyl methacrylate, t-butyl cyclohexyl acrylate, ort-butyl cyclohexyl methacrylate. Aryl acrylate and aryl methacrylatesalso can be used, for example, such as benzyl acrylate and benzylmethacrylate. Of course, mixtures of the two or more of the abovementioned monomers are also suitable.

In addition to alkyl acrylates or methacrylates, other polymerizablenon-silane-containing monomers, up to about 50% by weight of thepolymer, can be used in the acrylosilane polymer for the purpose ofachieving the desired properties such as hardness, appearance, marresistance, and the like. Exemplary of such other monomers are styrene,methyl styrene, acrylamide, acrylonitrile, methacrylonitrile, and thelike. Styrene can be used in the range of 0-50% by weight.

A suitable silane containing monomer useful in forming the acrylosilanepolymer is an alkoxysilane having the following structural formula:##STR1## wherein R is either CH₃, CH₃ CH₂, CH₃ O, or CH₃ CH₂ O; R₁ andR₂ are CH₃ or CH₃ CH₂ ; and R₃ is either H, CH₃, or CH₃ CH₂ ; and n is 0or a positive integer from 1 to 10. Preferably, R is CH₃ O or CH₃ CH₂ Oand n is 1.

Typical examples of such alkoxysilanes are the acrylatoalkoxy silanes,such as gamma-acryloxypropyltrimethoxy silane and the methacrylatoalkoxysilanes, such as gamma-methacryloxypropyltrimethoxy silane, andgamma-methacryloxypropyltris(2-methoxyethoxy) silane.

Other suitable alkoxy silane monomers have the following structuralformula: ##STR2## wherein R, R₁ and R₂ are as described above and n is apositive integer from 1 to 10.

Examples of such alkoxysilanes are the vinylalkoxy silanes, such asvinyltrimethoxy silane, vinyltriethoxy silane andvinyltris(2-methoxyethoxy) silane.

Other suitable silane containing monomers are acyloxysilanes, includingacrylatoxy silane, methacrylatoxy silane and vinylacetoxy silanes, suchas vinylmethyldiacetoxy silane, acrylatopropyltriacetoxy silane, andmethacrylatopropyltriacetoxy silane. Of course, mixtures of theabove-mentioned silane containing monomers are also suitable.

Consistent with the above mentioned components of the silane polymer, anexample of an organosilane polymer useful in the coating composition ofthis invention may contain the following constituents: about 15-25% byweight styrene, about 30-60% by weight methacryloxypropyltrimethoxysilane, and about 25-50% by weight trimethylcyclohexyl methacrylate.

One preferred acrylosilane polymer contains about 30% by weight styrene,about 50% by weight methacryloxypropyl trimethoxy silane, and about 20%by weight of nonfunctional acrylates or methacrylates such astrimethylcyclohexyl methacrylate, butyl acrylate, and iso-butylmethacrylate and any mixtures thereof.

Silane functional macromonomers also can be used in forming the silanepolymer. These macromonomers are the reaction product of a silanecontaing compound, having a reactive group such as epoxide orisocyanate, with an ethylenically unsaturated non-silane containingmonomer having a reactive group, typically a hydroxyl or an epoxidegroup, that is co-reactive with the silane monomer. An example of auseful macromonomer is the reaction product of a hydroxy functionalethylenically unsaturated monomer such as a hydroxyalkyl acrylate ormethacrylate having 1-4 carbon atoms in the alkyl group and anisocyanatoalkyl alkoxysilane such as isocyanatopropyl triethoxysilane.

Typical of such above mentioned silane functional macromonomers arethose having the following structural formula: ##STR3## wherein R, R₁,and R₂ are as described above; R₄ is H or CH₃, R₅ is an alkylene grouphaving 1-8 carbon atoms and n is a positive integer from 1-8.

Additional to the organosilane polymer, other film-forming and/orcrosslinking solution polymers may be included in the presentapplication. Examples include conventionally known acrylics,cellulosics, aminoplasts, urethanes, polyesters, epoxides or mixturesthereof. One preferred optional film-forming polymer is a polyol, forexample an acrylic polyol solution polymer of polymerized monomers. Suchmonomers may include any of the aforementioned alkyl acrylates and/ormethacrylates and, in addition, hydroxy alkyl acrylates ormethacrylates. The polyol polymer preferably has a hydroxyl number ofabout 50-200 and a weight average molecular weight of about1,000-200,000 and preferably about 1,000-20,000.

To provide the hydroxy functionality in the polyol, up to about 90% byweight, preferably 20 to 50%, of the polyol may comprises hydroxyfunctional polymerized monomers. Suitable monomers include hydroxy alkylacrylates and methacrylates, for example, hydroxy ethyl acrylate,hydroxy propyl acrylate, hydroxy isopropyl acrylate, hydroxy butylacrylate, hydroxy ethyl methacrylate, hydroxy propyl methacrylate,hydroxy isopropyl methacrylate, hydroxy butyl methacrylate, and thelike, and mixtures thereof.

Other polymerizable monomers may be included in the polyol polymer, inan amount up to about 50% by weight. Such polymerizable monomersinclude, for example, styrene, methylstyrene, acrylamide, acrylonitrile,methacrylonitrile, methacrylamide, methylol methacrylamide, methylolacrylamide and the like, and mixtures thereof.

One example of an acrylic polyol polymer comprises about 10-20% byweight of styrene, 40-60% by weight of alkyl methacrylate or acrylatehaving 1-6 carbon atoms in the alkyl group, and 10-50% by weight ofhydroxy alkyl acrylate or methacrylate having 1-4 carbon atoms in thealkyl group. One such polymer contains about 15% by weight styrene,about 29% by weight iso-butyl methacrylate, about 20% by weight2-ethylhexyl acrylate, and about 36% by weight hydroxy propylacrylate.

A key component of the coating composition of the present invention is,in addition to the above polymeric components, a dispersed polymer. Apolymer dispersed in an organic (substantially non-aqueous) medium havebeen variously referred to, in the art, as a non-aqueous dispersion(NAD) polymer, a microgel, a non-aqueous latex, or a polymer colloid.See generally, Poehlin et al., editor, SCIENCE AND TECHNOLOGY OF POLYMERCOLLOIDS, Volume 1, pages 40-50 (1983); El-Asser, editor, FUTUREDIRECTIONS IN POLYMER COLLOIDS, pages 191-227 (1987); Barrett,DISPERSION POLYMERIZATION IN ORGANIC MEDIA (John Wiley 1975). See alsoU.S. Pat. Nos. 4,147,688; 4,180,489; 4,075,141; 4,415,681; and4,591,533, hereby incorporated by reference. Microgel particles,necessarily cross-linked, have been used for years as impact modifiersfor plastics, as rheology controllers for coatings, and in basecoats, topermit wet-on-wet application of paints.

In general, the dispersed polymer of the present invention ischaracterized as a polymer particle dispersed in an organic media, whichparticle is stabilized by what is known as steric stabilization.According to the prior art, steric stabilization is accomplished by theattachment of a solvated polymeric or oligomeric layer at the particlemedium interface. The problem of providing a steric barrier has beenconsidered in two parts: first, the selection of the soluble polymerwhich comprises the solvate sheath surrounding each particle and,secondly, the method of attaching or anchoring this polymer to theparticle surface. It is also known that to increase the stability of thea dispersed polymer, particularly to strong solvents, or to ensure thatthe stabilizer is not desorbed or displaced, the anchor group may becovalently linked to the particle. This has been achieved byincorporating into the anchor group a reactive group, for example aglycidal group which can react with a complementary group in thedispersed polymer, for example a carboxylic acid.

In the dispersed polymers of the present composition, the dispersedphase or particle, sheathed by a steric barrier, will be referred to asthe "macromolecular polymer" or "core." The stabilizer forming thesteric barrier, attached to this core, will be referred to as the"macromonomer chains" or "arms."

The dispersed polymers of the present invention solve the problem ofcracking heretofor associated with silane coatings. These dispersedpolymers, to reduce cracking to the desired minimum, must be used inhigher amounts than dispersed polymers are typically used for otherpurposes. For example, while microgels have been used in basecoats forflow control at levels of not more than about 5%, the present dispersedpolymers are used in an amount varying from about 10 to 60% by weight,preferably about 15 to 40%, more preferably about 20 to 30%, of thetotal binder in the composition. The ratio of the silane polymer to thedispersed polymer component of the composition suitably ranges from 5:1to 1:2, preferably 4:1 to 1:1. These relatively high concentrations ofdispersed polymers, in the present composition, is made possible by thepresence of reactive groups on the arms of the dispersed polymer, whichreactive groups make the polymers compatible with the continuous phaseof the system.

The dispersed polymer contains suitably about 10-90%, preferably 50-80%,by weight, based on the weight of the dispersed polymer, of a highmolecular weight core having a weight average molecular weight of about50,000-500,000. The preferred average particle size is 0.1 to 0.5microns. The arms, attached to the core, make up about 90-10%,preferably 20-59%, by weight of the dispersed polymer, and have a weightaverage molecular weight of about 1,000-30,000, preferably 1,000 to10,000.

Preferably, the macromolecular core of the dispersed polymer iscomprised of polymerized ethylenically unsaturated monomers. Suitablemonomers include styrene, alkyl acrylate or methacrylate, ethylenicallyunsaturated monocarboxylic acid, and/or silane containing monomomers.Such monomers as methyl methacrylate contribute to a high Tg (transitionglass temperature) dispersed polymer, whereas such "softening" monomersas butyl acrylate or 2-ethylhexylacrylate contribute to a low Tgdispersed polymer. Other optional monomers are hydroxyalkyl acrylates ormethacrylates or acrylonitrile. Such functional groups as hydroxy in thecore can react with silane groups in the organosilane polymer to produceadditional bonding within the film matrix. If the core is crosslinked,allyl acrylate or allyl methacrylate, which link with each other, can beused or an epoxy functional monomer such as glycidyl acrylate ormethacrylate can be used, which will react with the monocarboxylic acidfunctional monomers to crosslink the core.

Preferably, there is silane functionality, for crosslinking purposes, inthe core, which functionality may be provided by a small amount of oneor more of the silane containing monomers mentioned above with respectto the film forming organosilane polymer. Preferably, the silanefunctionality is the primary means, more preferably the sole means, ofcrosslinking in the core. Suitably about 2 to 10%, preferably about lessthan 5% of the monomers making up the macromolecular core are silanemonomers capable of crosslinking between themselves. Thus, crosslinkingoccurs by siloxane bonding (--Si--O--Si--). This silane crosslinkingenables the core to behave as a non-crosslinked polymer before cure forgood flow during application, resulting in improved appearance. The corecan crosslink during and after curing, upon exposure to H₂ O and/or heatduring curing and/or exposure to humidity in the environment aftercuring. A further advantage of silane being present in the core is thatthe cured film does not blush when exposed to humidity, which blushingwas found to occur without the presence of silane. If the case ispre-crosslinked (before curing) by other means, such as acid/epoxy ordiacrylates, then humidity sensitivity may be eliminated but the systemmay have poor flow and appearance.

The reason that the dispersed polymer in the present coating compositioneliminates the cracking problem which silane-containing film formingpolymers are otherwise prone is not known for certain. Although notwishing to be bound by theory, one hypothesis is that the dispersedpolymer provides reinforcement, which enables the coating to withstandstress and/or U.V. degradation. Such reinforcement may also prevent thepropogation of cracking. Another hypothesis is that the dispersedpolymer, with its macromolecular coil or core, provides a certain amountof sponginess and flexibilty to the coating, that is, the macromolecularcore may be able to contract and expand, especially with low volatileorganic content. This so-called sponginess compensate to some extent forthe points, or concentrated areas of silane bonding. Silane tends tobecome very tightly bound, since each silane moiety potentially can becrosslinked at three sites and a number of silane moieties can becomeextended in a silane matrix. Without the dispersed polymer, anoverconcentration of silane crosslinking may result in stress cracking.

As mentioned above, it is preferred that the macromolecular core of thedispersed polymer has a low amount of crosslinking within themacromolecular core and, most preferably, the core has zeropre-crosslinking. This means there is no crosslinking in solution,before the composition is cured or baked. Without crosslinking, themacromolecular core is capable of uncoiling to some extent and thereforehas a better tendency to flow, an advantage in spray appplication of thecoating composition. Some degree of crosslinking may be desirable, forexample, in order to derive the macromolecular core polymer from shorterchains. However, in general, the greater the crosslinking, the moretightly bound together the polymer and the less its ability to preventcracking of the coating. Because limited or no pre-crosslinking in themacromolecular core of the dispersed polymer is desired, dispersedpolymers which are relatively highly crosslinked, such as structuredStar polymers, while useful to some extent, may be less preferred. Starpolymers, such as in U.S. Pat. No. 4,810,756 to Spinelli, herebyincorporated by reference, but with reactive arms as disclosed herein,also have relatively small cores, compared to the preferred dispersedpolymers.

A distinctive feature of the dispersed polymers of the present inventionis the presence of macromonomer arms which contain hydroxy groups whichare adapted to react with the organosilane polymer of the presentcomposition. It is not known with certainty what portion of the thesehydroxy functional groups do, in fact, react with the organosilanepolymer, because of the numerous and complicated sets of reactions whichmay occur during baking and curing of the composition, especially ifadditional film-forming binders are present. However, it may be saidthat a substantial portion of these functionalities in the arms,preferably the majority therof, do in actuality react and crosslink withthe film-former of the composition, which in some cases may exclusivelyconsist of an organosilane polymer. Dispersed polymers havinghydroxy-containing reactive arms have been disclosed in U.S. Pat. No.4,591,533 to Antonelli et al.

The arms of the dispersed polymer should be anchored securely to themacromolecular core. For this reason, the arms preferably are anchoredby covalent bonds. The anchoring must be sufficent to hold the arms tothe dispersed polymer after they react with the film-former polymer. Forthis reason, the conventional method of anchoring by adsorption of thebackbone portion of a graft polymer may provide insufficent anchoring.

As indicated above, the arms or macromonomers of the dispersed polymerserve to prevent the core from flocculating by forming what is referredto in the art as a steric barrier. The arms, typically in contrast tothe macromolecular core, are believed capable, at least temporarily, ofbeing solvated in the organic solvent carrier or media of thecomposition. They may therefore be in a chain-extended configuration andtheir hydroxy functional groups are therefore relatively readilyavailable to reaction with the silane groups of the film forming silanecontaining polymer. Such arms suitably comprise about 3 to 30% byweight, preferably 10 to 20%, based on the weight of macromonomer, ofpolymerized ethylenically unsaturated hydroxy functionality containingmonomers, and about 70-95% by weight, based on the weight of themacromonomer, of at least one other polymerized ethylenicallyunsaturated monomer without such crosslinking functionality.Combinations of such hydroxy monomers with other lesser amounts ofcrosslinking functional groups, such as silane or epoxy, on the arms arealso suitable, although it is noted that hydroxy and silane groups havelimited compatibility and are preferably not on the same macromonomerchain.

As an example, the macromonomer arms attached to the core may containpolymerized monomers of alkyl methacrylate, alkyl acrylate, each having1-12 carbon atoms in the alkyl group, as well as glycidyl acrylate orglycidyl methacrylate or ethylenically unsaturated monocarboxylic acidfor anchoring and/or crosslinking. Typically useful hydroxy containingmonomers are hydroxy alkyl acrylates or methacrylates as describedabove.

A preferred composition for a dispersed polymer that has hydroxyfunctionality comprises a core consisting of about 25% by weight hydroxyethyl acrylate, about 4% by weight methacrylic acid, about 46.5% byweight methyl methacrylate, about 18% by weight methyl acrylate, about1.5% by weight glycidyl methacrylate and about 5% styrene. Themacromonomer attached to the core contains 97.3% by weight prepolymerand about 2.7% by weight glycidyl methacrylate, the latter forcrosslinking or anchoring.

A preferred prepolymer contains about 28% by weight butyl methacrylate,about 15% by weight ethyl methacrylate, about 30% by weight butylacrylate, about 10% by weight hydroxyethyl acrylate, about 2% by weightacrylic acid, and about 15% by weight styrene.

The dispersed polymer may be produced by conventionally knownprocedures. For example, it has been disclosed that such polymers may beproduced by a process of dispersion polymerization of monomers, in anorganic solvent, in the presence of a steric stabilizer for theparticles. The procedure has been described as basically one ofpolymerizing the monomers in an inert solvent in which the monomers aresoluble but the resulting polymer is not soluble, in the presence of adissolved amphiteric stabilizing agent. Such procedures have beenextensively disclosed in both the patent and non-patent literature, forexample, see the above cited references regarding dispersed polymers ingeneral, or U.S. Pat. No. 4,220,679 and PAINT AND SURFACE COATING:THEORY AND PRACTICE, ed. R. Lambourne (Ellis Horwood Limited 1987). Asillustrated in the examples below, the macromonomer arms can be preparedby cobalt catalyzed special chain transfer (SCT) polymerization, grouptransfer polymerization (GTP), or free radical polymerization.

Optionally, the present coating composition may optionally furtherinclude, particularly in conjunction with an optional polyol polymer, anadditional crosslinking agent, for example conventionally knownmonomeric or polymeric alkylated melamine formaldehyde resin that ispartially or fully alkylated. One preferred crosslinking agent is amethylated and butylated or isobutylated melamine formaldehyde resinthat has a degree of polymerization of about 1-3 Generally, thismelamine formaldehyde resin contains about 50% butylated groups orisobutylated groups and 50% methylated groups. Such crosslinking agentstypically have a number average molecular weight of about 300-600 and aweight average molecular weight of about 500-1500. Examples ofcommercially available resins are "Cymel" 1168, "Cymel"1161, "Cymel"1158, "Resimine" 4514 and "Resimine" 354. Preferably, the crosslinkingagent is used in the amount of about 5-50% by weight, based on theweight of the binder of the composition. Other crosslinking agents areurea formaldehyde, benzoquanamine formaldeyde and blockedpolyisocyanates.

A catalyst is typically added to catalyze the crosslinking of the silanemoieties of the silane polymer with itself and with other components ofthe composition, including the dispersed polymer. Typical of suchcatalysts are dibutyl tin dilaurate, dibutyl tin diacetate, dibutyl tindioxide, dibutyl tin dioctoate, tin octoate, aluminum titanate, aluminumchelates, zirconium chelate and the like. Tertiary amines and acids orcombinations therof are also useful for catayzing silane bonding.Preferably, these catalysts are used in the amount of about 0.1 to 5.0%by weight of the composition.

To improve weatherability of a clear finish produced by the presentcoating composition, an ultraviolet light stabilizer or a combination ofultraviolet light stabilizers can be added in the amount of about 0.1-5%by weight, based on the weight of the binder. Such stabilizers includeultraviolet light absorbers, screeners, quenchers, and specific hinderedamine light stabilizers. Also, an anitoxidant can be added, in the about0.1-5% by weight, based on the weight of the binder.

Typical ultraviolet light stabilizers that are useful includebenzophenones, triazoles, triazines, benzoates, hindered amines andmixtures thereof. Specific examples of ultraviolet stabilizers aredisclosed in U.S. Pat. No. 4,591,533, the entire disclosure of which isincorporated herein by reference.

The composition may also include other conventional formulationadditives such as flow control agents, for example, such as Resiflow® S(polybutylacrylate), BYK 320 and 325 (high molecular weightpolyacrylates); rheology control agents, such as funed [fused?] silica;water scavengers such as tetrasilicate, trimethyl orthoformate, triethylorthoformate and the like.

When the present composition is used as a clearcoat (topcoat) over apigmented colorcoat (basecoat) to provide a colorcoat/clearcoat finish,small amounts of pigment can be added to the clear coat to eliminateundesirable color in the finish such as yellowing.

The present composition also can be pigmented and used as the colorcoat,or as a monocoat or even as a primer or primer surfacer. The compositionhas excellent adhesion to a variety of substrates, such as previouslypainted substrates, cold rolled steel, phosphatized steel, and steelcoated with conventional primers by electrodeposition. The presentcomposition exhibits excellent adhesion to primers, for example, thosethat comprise crosslinked epoxy polyester and various epoxy resins, aswell as alkyd resin repair primers. The present compositon can be usedto coat plastic substrates such as polyester reinforced fiberglass,reaction injection-molded urethanes and partially crystallinepolyamides.

When the present coating composition is used as a basecoat, typicalpigments that can be added to the composition inculde the following:metallic oxides such as titanium dioxide, zinc oxide, iron oxides ofvarious colors, carbon black, filler pigments such as talc, china clay,barytes, carbonates, silicates and a wide variety of organic coloredpigments such as quinacridones, copper phthalocyanines, perylenes, azopigments, indanthrone blues, carbazoles such as carbozole violet,isoindolinones, isoindolones, thioindigo reds, benzimidazolinones,metallic flake pigments such as aluminum flake and the like.

The pigments can be introduced into the coating composition by firstforming a mill base or pigment dispersion with any of the aforementionedpolymers used in the coating composition or with another compatablepolymer or dispersant by conventional techniques, such as high speedmixing, sand grinding, ball milling, attritor grinding or two rollmilling. The mill base is then blended with the other constituents usedin the coating composition.

Conventional solvents and diluents are used to disperse and/or dilutethe above mentioned polymers to obtain the present coating composition.Typical solvents and diluents include toluene, xylene, butyl acetate,acetone, methyl isobutyl ketone, methyl ethyl ketone, methanol,isopropanol, butanol, hexane, acetone, ethylene glycol, monoethyl ether,VM and P naptha, mineral spirits, heptane and other aliphatic,cycloaliphatic, aromatic hydrocarbons, esters, ethers and ketones andthe like.

The coating composition can be applied by conventional techniques suchas spraying, electrostatic spraying, dipping, brushing, flowcoating andthe like. The preferred techniques are spraying and electrostaticspraying. After application, the composition is typically baked at100°-150° C. for about 15-30 minutes to form a coating about 0.1-3.0mils thick. When the composition is used as a clearcoat, it is appliedover the colorcoat which may be dried to a tack-free state and cured orpreferably flash dried for a short period before the clearcoat isapplied. The colorcoat/clearcoat finish is then baked as mentioned aboveto provide a dried and cured finish.

It is customary to apply a clear topcoat over a basecoat by means of a"wet-on-wet" application, i.e., the topcoat is applied to the basecoatwithout curing or completely drying the basecoat. The coated substrateis then heated for a predetermined time period to allow simultaneouscuring of the base and clear coats.

Upon curing of clear topcoat compositions of the present invention, aportion of the silane containing polymer may migrates and stratifies tothe top of the clearcoat, particluarly when the organosilane polymer isused in combination with a polyol, so as to produce a durable,weather-resistant clearcoat. Such stratification has been shown byelectron scanning chemical analysis (ESCA) of a cross section of thecured layer of topcoat.

The coating composition can be formulated as a one-package system thathas an extended shelf life.

The following Examples illustrate the invention. All parts andpercentages are on a weight basis unless otherwise indicated.

EXAMPLE 1

An organosilane polymer solution A is prepared by charging the followingconstituents into a polymerization reactor equipped with a heat sourceand a reflux condensor:

    ______________________________________                                                             Parts by                                                                      weight                                                   ______________________________________                                        Portion I                                                                     "Solvesso" 100          75.00                                                 Portion II                                                                    Methacryloxypropyltrimethoxy silane                                                                  300.00                                                 Styrene monomer        173.00                                                 Isobutyl methacrylate monomer                                                                        103.86                                                 "Solvesso" 100          45.02                                                 Portion III                                                                   2,2-(2-methyl butane nitrile)                                                                         57.32                                                 "Solvesso" 100          85.80                                                 Total                  840.00                                                 ______________________________________                                    

The "Solvesso" 100 is a conventional aromatic hydrocarbon solvent.Portion I is charged into the reactor and heated to its refluxtemperature. Portion II, containing the monomers for the organosilanepolymer, and Portion III, containing the polymerization initiator, areeach premixed and then added simultaneously to the reactor while thereaction mixture is held at its reflux temperature. Portion II is addedat a uniform rate over a 6 hour period and Portion II is added at auniform rate over a 7 hour period. After Portion II is added, thereaction mixture is held at its reflux temperature for an additionalhour. The resulting acrylosilane polymer solution is cooled at roomtemperature and filtered.

The resulting acrylosilane polymer solution has a polymer solids contentof about 70%, the polymer has a weight average molecular weight of about3,000, and has the following constituents: 30% styrene, 18% isobutylmethacrylate, and 52% methacryloxypropyl trimethoxysilane.

EXAMPLE 2

A hydroxy functional non-aqueous sterically stabilized dispersed polymeris prepared by charging the following components into a reactor:

    ______________________________________                                                               Parts by                                                                      Weight                                                 ______________________________________                                        Portion I                                                                     Isopropanol              179.26                                               Acrylic polymer solution 2254.05                                              (52% solids of an acrylic polymer                                             of 15% styrene, 28% butyl methacrylate,                                       30% butyl acrylate, 10% hydroxy ethyl                                         acrylate, 2% acrylic acid and 15% ethyl                                       methacrylate having a weight average                                          molecular weight of 10,000 in a solvent                                       mixture of 82.2% xylene and 17.8% butanol)                                    Mineral spirits          255.65                                               Heptane                  1912.46                                              Portion II                                                                    Heptane                   28.75                                               t-Butyl peroctoate        4.68                                                Portion III                                                                   Methyl methacrylate monomer                                                                            1459.69                                              Hydroxyethyl acrylate monomer                                                                          784.81                                               Styrene monomer          156.97                                               Portion IV                                                                    Acrylic polymer solution 1126.52                                              (53% solids of an acrylic polymer                                             of 15% styrene, 28% butyl methacrylate,                                       30% butyl acrylate, 10% hydroxy ethyl                                         acrylate, 2% acrylic acid and 15% ethyl                                       methacrylate, 2.7% glycidyl methacrylate                                      having a weight average molecular weight                                      of 10,000 in a solvent mixture of 82.2%                                       xylene and 17.8% butanol)                                                     Methyl methacrylate monomer                                                                            125.57                                               Methyl acrylate monomer  565.06                                               Glycidyl methacrylate monomer                                                                           47.05                                               Heptane                   17.25                                               Portion V                                                                     Mineral Spirits          638.63                                               t-Butyl peroctoate        47.14                                               Isobutanol               127.31                                               Portion VI                                                                    t-Butyl peroctoate        30.96                                               Isobutanol               255.65                                               Portion VII                                                                   Heptane                  167.25                                               Total                    10,184.71                                            ______________________________________                                    

Portion I is charged into the reaction vessel and heated to its refluxtemperature. Then Portion II is added to the reaction vessel mixed andheld at reflux temperature for 2 minutes. Then Portions III and IV areadded simultaneously with Portion V, over a 210 minute period, to thereaction vessel while maintaining the resulting reaction mixture at itsreflux temperature. Then the mixture is held at its reflux temperaturefor an additional 45 minutes. Portion VI is added over a 90 minuteperiod while maintaining the reaction mixture at its reflux temperatureand then held at this temperature for an additional 90 minutes. PortionVII is added and excess solvent is stripped off to give a 60% solidsdispersion.

The resulting polyester dispersed polymer has a core having a weightaverage molecular weight of about 100,000-200,000 and arms attached tothe core having a weight average molecular weight of about10,000-15,000.

EXAMPLE 3

An acrylic polyol resin solution is prepared by charging the followingconstituents into a polymerization reactor equipped with a heat sourceand a reflux condenser:

    ______________________________________                                                         Parts by                                                                      Weight                                                       ______________________________________                                        Portion I                                                                     n-Pentyl propionate                                                                              501.00                                                     Portion II                                                                    Styrene            360.00                                                     Isobutyl methacrylate                                                                            696.00                                                     2-Ethylhexyl acrylate                                                                            480.00                                                     Hydroxypropyl acrylate                                                                           864.00                                                     n-Pentylpropionate 285.00                                                     Portion III                                                                   t-Butyl peroctoate  60.00                                                     n-Pentyl propionate                                                                               60.00                                                     Total              3306.00                                                    ______________________________________                                    

Portion I is charged into the reactor and is heated to its refluxtemperature of about (160°-163° C.). Portions II and III are eachpremixed and then added simultaneously to the reactor while the reactionmixture is held at its reflux temperature. Portion II is added at auniform rate over a 6 hour period and Portion III is added at a uniformrate over a 7 hour period. After Portion III is added, the reactionmixture is held at its reflux temperature for an additional hour. Theresulting acrylic polyol resin solution is cooled at room temperatureand filtered.

The resulting acrylic polyol resin solution is 70% by weight of polymersolids. The polymer has a weight average molecular weight of about 6,000and a hydroxyl number of about 150-160. It constitutes the following:15% styrene, 29% isobutyl methacrylate, 20% 2-ethylhexyl methacrylate,and 36% hydroxypropyl acrylate.

EXAMPLE 4

A coating composition is prepared by blending together the followingconstituents:

    ______________________________________                                                               Parts by                                                                      Weight                                                 ______________________________________                                        Portion I                                                                     Xylene                   163.00                                               2(3-hydroxy-3,5,-ditertamylphenyl                                                                      113.20                                               amylphenyl) benzotriazole                                                     Hindered amine U.V. light stabilizer                                                                   147.80                                               solution (40% solution in xylene of                                           8-acetyl-3-dodecyl - 7, 7, 9, 9-                                              tetramethyl-2, 3, 8-triazaspiro (4,5)-                                        decane-2,4 dione)                                                             Baysilon Oil Solution     4.10                                                (72.8 parts Baysilone Fluid OL and                                            655.2 parts xylene)                                                           Portion II                                                                    Methylated/butylated melamine                                                                          2068.50                                              formaldehyde resin (fully butylated                                           and methylated melamine formaldehyde                                          resin having a butoxy/methoxy ratio                                           of 1:1 and a degree of polymerization                                         of about 1-1.2)                                                               Acrylic polyol resin solution                                                                          4054.30                                              Blocked sulfonic acid solution                                                                         236.40                                               (33% solids in methanol of dodecyl benzene                                    sulfonic acid blocked with dimethyl                                           oxazolidine, molar ratio of acid: dimethyl                                    oxazolidine is 1.52:1)                                                        Dispersed polymer (prepared above)                                                                     985.40                                               Acrylosilane polymer solution A                                                                        3439.00                                              (prepared above)                                                              Dibutyl tin dilaurate     65.00                                               Portion III                                                                   Methanol                 203.80                                               "Solvesso" 100 - hydrocarbon solvent                                                                   458.50                                               Total                    11,939.00                                            ______________________________________                                    

The constituents of Portion I are added in the order shown to a mixingvessel and agitated until solution is complete. Portion II is added tothe vessel and mixed for 30 minutes. Portion III is added and mixed for30 minutes. The resulting clear coating composition has 70% solidscontent.

The resulting composition is sprayed onto primer coated phosphatizedsteel panels that were coated with a solvent base pigmented acrylicpolymer basecoating composition. The composition is sprayed onto thepanels before the basecoating is baked. The panels are baked at 120° C.for 30 minutes and a clear coat about 2 mils thick is formed on eachpanel. The clear coating has a hardness of 8 knoops, a gloss measured at20° C. of 95. The coating has excellent outdoor weatherability andresistance to environmental attack, good mar and scratch resistance,good humidity resistance as determined by the Cleveland Humidity testand good chip resistance as determined by a gravelometer test.

EXAMPLE 5

An acrylosilane polymer solution B is prepared by first forming a silanecontaing macromonomer and then reacting the macromonomer with acrylicmonomers.

The macromonomer is prepared by charging the following constituents intoa reactor equipped as above:

    ______________________________________                                                           Parts by                                                                      Weight                                                     ______________________________________                                        Portion I                                                                     Y-9030 (isocyanatopropylmethoxy                                                                    750.0                                                    silane)                                                                       Xylene               300.0                                                    Portion II                                                                    Hydroxyethyl acrylate monomer                                                                      340.0                                                    Total                1390.0                                                   ______________________________________                                    

Portion I is heated to about 120° C. and Portion II is slowly added overa 1 hour period with constant mixing. The reaction mixture is held atthe above temperature for about 1 hour and the isocyanate level ischecked by infrared analysis. When the isocyanate level reaches zero,the reaction is stopped and the resulting macromonomer solution iscooled to room temperature.

Acrylosilane polymer solution B is prepared by charging the followingconstituents into a reactor as equipped above:

    ______________________________________                                                              Parts by                                                                      Weight                                                  ______________________________________                                        Portion I                                                                     "Solvesso" 100          430.0                                                 Portion II                                                                    Macromonomer solution (prepared above)                                                                1826.0                                                Styrene monomer         765.0                                                 Methyl methacrylate monomer                                                                           153.0                                                 Butyl methacrylate monomer                                                                            153.0                                                 2-Ethylhexyl methacrylate monomer                                                                     153.0                                                 "Solvesso" 100          170.0                                                 Portion III                                                                   2,2-(2 methyl butane nitrile)                                                                         100.0                                                 "Solvesso" 100          300.0                                                 Total                   4050.0                                                ______________________________________                                    

Portion I is charged into the reactor and heated to its refluxtemperature. Portions II and III are premixed and slowly added to thereactor while maintaining the reaction mixture at its refluxtemperature. Portion II is a added over a 6 hour period and Portion IIIis added over a 7 hour period. The reaction mixture is held at itsreflux temperature for an additional hour and then cooled to roomtemperature.

The resulting acrylosilane polymer solution has a polymer solids contentof about 66%. The polymer has a weight average molecular weight of about6,000, and has the following constituents: 53% macromonomer, 29%styrene, 6% methyl methacrylate, 6% butyl methacrylate, and 6%2-ethylhexyl methacrylate.

EXAMPLE 6

An acrylosilane polymer solution C is prepared by cobalt special chaintransfer (SCT) by charging the following constituents into a heatedreactor flask of five liter volume fitted with a water cooled condensor,stirrer, 2 feed metering pumps and a thermometer:

    ______________________________________                                                               Parts by                                                                      Weight                                                 ______________________________________                                        Portion I                                                                     "Solvesso" 100           120.00                                               Ethylene Glycol Monobutyl Ether Acetate                                                                120.00                                               Xylene                   150.00                                               Portion II                                                                    gamma-methacryloxypropyltrimethoxy                                                                     39.67                                                silane                                                                        Styrene                  28.33                                                Isobutyl methacrylate    45.33                                                Co(DMG-BF.sub.2).sub.2   0.05                                                 VAZO 67                  2.74                                                 Portion III                                                                   gamma-methacryloxypropyltrimethoxy                                                                     847.83                                               silane                                                                        Styrene                  605.42                                               Isobutyl methacrylate    968.67                                               Portion IV                                                                    VAZO 67                  17.25                                                "Solvesso"               100.00                                               Ethylene glycol monobutyl ether acetate                                                                100.00                                               Xylene                   100.00                                               Portion V                                                                     t-Butyl Peroxyacetate    10.00                                                Xylene                   60.00                                                ______________________________________                                    

Portion I, containing organic solvents, is charged into the reactorflask and heated under a nitrogen atmosphere to its reflux temperature.Portion II, containing the acrylosilane monomers and an initiator (acobalt chelate of dimethylglycol and boron difluoride), is added to therefluxing solvent over a 10 minute period. After the 10 minute period,Portion III, containing additional monomers, and Portion IV, containingadditional solvent, are each premixed and then added simultaneously tothe reactor while the reaction mixture is held at its refluxtemperature. Portion III is added at a uniform rate over a period of 360minutes and Portion IV is added at a uniform rate over a period of 390minutes. Then, Portion V, containing an initiator to kill the cobaltchain transfer, is fed over a 20 minute period. After Portion V isadded, the reaction mixture is held at its reflux temperature for anadditional 30 minutes. The resulting acrylosilane polymer solution iscooled at room temperature and filtered. The polymer has a weightaverage molecular weight of about 10,000-12,000 and constitutes 29%styrene, 30% isobutyl methacrylate and 41% methacryloxypropyltrimethoxysilane.

EXAMPLE 7

An acrylosilane polymer solution D is prepared by a group transferprocess (GTP) as follows. To a four neck 3 liter flask, fitted with astirrer, condenser, two feed pumps, thermometer and nitrogen inlet isadded 950 g toluene, 136 g methyl methacrylate, 106 g butylmethacrylate, 118 g trimethoxysilylpropyl methacrylate and 46.2 gtrimethoxysilylpropyl dimethyl ketene. The reaction mixture is cooled to5° C. and 4 ml of tetrabutyl ammonium m-chlorobenzoate catalyst is addedover 90 minutes. The catalyst feed is temporarily interrupted during thereaction exotherm. When the exotherm subsides, the catalyst feed isresumed together with a monomer feed, over 40 minutes, of 220 g methylmethacrylate, 212 g butyl methacrylate and 237 g trimethoxysilylpropylmethacrylate. After completing all the addition, the reaction mixture isheld for an additional half hour, after which 45 g methanol, for killingthe ketene initiator, is added to the reaction mixture. The resultingpolymer solution constitutes 35% methyl methacrylate, 31% butylmethacrylate, and 34% methacryloxypropyl trimethoxysilane.

EXAMPLE 8

The following components are used in preparing an acrylosilane solutionpolymer by free radical polymerization.

    ______________________________________                                                            Parts by                                                                      Weight                                                    ______________________________________                                        Portion I                                                                     "Solvesso" 100        726.4     g                                             Portion II                                                                    Methacryloxypropyltrimethoxy silane                                                                 1380.3    g                                             Styrene               500.      g                                             Methyl methacrylate monomer                                                                         424.7     g                                             2-Ethylhexyl acrylate 159.2     g                                             Butyl methacrylate monomer                                                                          159.2     g                                             Hydrocarbon ("Napoleum" 145A)                                                                       81.8      g                                             Portion III                                                                   "Lupensol" 70         70.       g                                             Hydrocarbon ("Napoleum" 145A)                                                                       199.3     g                                             Portion IV                                                                    Hydrocarbon ("Napoleum" 145A)                                                                       27.2      g                                             Portion V                                                                     Hydrocarbon ("Napoleum" 145A)                                                                       9.1       g                                             ______________________________________                                    

Portion I, containing organic solvent, is charged to the reaction flaskand heated to reflux. Portion II, containing the monomers for theacrylosilane polymer, and Portion III, containing a t-butyl initiator,are added simultaneously. Portion II is added over a 6 hour period, andPortion III is added over a 7 hour period. After Portion II is added,Portion IV is added immediately. After Portion III is added, Portion Vis added immediately. Heating is continued at reflux for one additionalhour after all the portions have been added. The reaction mixture isthen cooled and filtered.

EXAMPLE 9

A dispersed (NAD) polymer A is prepared as follows. The macromonomerportion is prepared by a group transfer procedure.

Macromonomer A: To a four neck 3 liter flask, is fitted a stirrer,condenser, two feed pumps, thermometer and nitrogen inlet. To the flaskis added 840 g of toluene, 100.3 g 2-ethylhexyl methacrylate, 75.4 gisobutyl methacrylate, 16.4 g hydroxyethyl methacrylate and 38.6 gtrimethoxysilylpropyl dimethylketene. The reaction mixture is cooled to5° C. and the addition of 6.0 g tetrabutylammonium m-chlorobenzoatecatalyst over 90 minutes is started. The catalyst feed is temporarilyinterrupted during the reaction exotherm. When the exotherm subsides,the catalyst feed is resumed together with a monomer feed over 40minutes, comprising 202.1 g 2-ethylhexyl methacrylate, 136.7 g isobutylmethacrylate and 29.7 g hydroxyethyl methacrylate. A second monomer feedof 23.0 g allyl methacrylate is then added to the reactor. Aftercompleting all the additions, the reaction mixture is held for anadditional 30 min., after which 3.0 g methanol is added to the reactionmixture.

Macromolecular Core: A reactor is charged with 248.3 g of macromonomer Aabove and 251.94 g heptane and heated to reflux under N2. At reflux isadded 0.41 g tert-butylperoctoate, an initiator, followed with monomerand initiator feeds added over 210 minutes. The monomer feed is asfollows: 20.6 heptane, 41.58 g stryrene, 54.25 g Methyl acrylate, 138.61g methyl methacrylate, 13.86 g methacryloxypropyl trimethoxysilane,27.12 g acrylonitrile, 133.7 g macromonomer A. The initiator feed is asfollows: 48.38 g heptane and 4.16 g TBPO (tertiary butyl peroxide). Thereaction is held at reflux for 45 minutes. A scavenger mix of 18.04 gheptane and 2.72 g TBPO is then added over 90 minutes. The reaction isheld at reflux for 60 minutes and then distilled to 55% solids.

EXAMPLE 10

This example illustrates a dispersed or NAD Polymer B, in which themacromonomer is prepared by special chain transfer:

Macromonomer B: To a reactor is added 100.92 g butyl acrylate, 100.92 gisobutyl methacrylate, 600.62 g 2-ethylhexyl methacrylate , 110.24 ghydroxyethyl methacrylate and 611.94 g toluene. The mixture is heated toreflux under N₂. At reflux is added a mixture of 178.43 g butylacrylate, 178.45 g isobutylmethacrylate, 42.93 g toluene, 1.17 g VAZO 88(a nitrile initiator) and 30 ppm Co(DMG-BF2)2 catalyst over 10 minutes.To the reactor is then fed a mixture of 190.61 g isobutylmethacrylate,621.93 g 2-ethylhexyl methacrylate, 120.66 g methacryloxypropyltrimethoxysilane, 4.13 g VAZO 88 and 86.08 g toluene over a period of240 minutes. This is followed with a scavenger feed of 108.01 g tolueneand 2.01 g VAZO 88 for 60 minutes. The reaction is the held at refluxfor 90 minutes. Finally, 251.21 g toluene is added.

Macromolecular Core: To a reactor is charged 142.4 g of macromonomer Bas prepared above and 251.94 g heptane. This is heated to reflux underN₂. At reflux is added 0.41 g tert-butylperoctoate, followed withmonomer and initiator feeds added over 210 minutes. The monomer feed isas follows: 20.6 g heptane, 41.58 g styrene, 54.25 g methylmethacrylate, 138.61 g methyl acrylate, 13.86 g methaacryloxypropyltrimethoxysilane, 27.12 g acrylonitrile, 76.68 g of macromonomer B. Theinitiator feed is as follows: 48.38 g heptane and 4.16 g TBPO. Thereaction feed is held at reflux for 45 minutes and then a scavenger mixis started of 18.04 g heptane and 2.72 g TBPO over 90 minutes. Thereaction mixture is held at reflux for 60 minutes and distilled to 55%solids.

EXAMPLE 11

This example illustrates a dispersed (NAD) Polymer C prepared by a freeradical procedure:

Macromonomer C: To a reactor is added 195.91 g xylene which is heated toreflux under N₂. At reflux is added a mixture of 213.0 gbutylmethacrylate, 221.21 g butyl acrylate, 49.54 g hydroxyethylacrylate, 11.6 g methyl methacrylate, and 6.0 g xylene over 240 mins.with the initiator feed. The initiator feed consists of 30.0 g xylene,41.55 g butanol and 37.18 g TBPO and is fed to the reactor with monomerfeed over 270 mins. To the reactor is added a mix of 0.02 g butylcatechol, 0.21 g isopropanol, 8.8 g glycidyl methacrylate and 3.0 gxylene. A a mix of 0.12 g dimethylethylamine and 0.5 g xylene is addedto the reactor, held for 90 mins. and cooled quickly to below 176° F.

Macromolecular core C: To a reactor is charged 142.4 g macromonomer Cprepared as above and 251.94 g heptane. The mixture is heated to refluxunder N₂. At reflux is added 0.41 g tert-butylperoctoate, followed withmonomer and initiator feeds added over 210 minutes. The monomer feedconsists of the following: 20.6 g heptane, 41.58 g styrene, 68.11 gmethyl methyl methacrylate, 138.61 g methyl acrylate, 27.12 gacrylonitrile, and 76.68 g of macromonomer C as prepared above. Theinitiator feed consisted of the following: 48.38 g heptane and 4.16 gTBPO. The reaction is held at reflux for 45 minutes and then is added ascavenger mix of 18.04 g heptane and 2.72 g TBPO over 90 minutes. Thereaction is held at reflux for 60 minutes and then distilled to 55%solids.

EXAMPLE 12

This example illustrates a clearcoat composition according to thepresent invention. The following ingredients were added with mixing anda nitrogen blanket:

    ______________________________________                                        Polymer B           320.00      gm                                            NAD A               162.00      gm                                            Tin 1130            7.50        gm                                            Tin 440 (40% sol. in Xylene)                                                                      7.50        gm                                            "Byk" 325           0.60        gm                                            Trimethyl orthoformate                                                                            1.00        gm                                            "Fascat" 4020       6.00        gm                                            "Solvesso" 100      35.00       gm                                            ______________________________________                                    

In the above list, tin 1130 and tin 440 are U.V. screeners, "Byk" 325 isa flow agent, trimethylorthoformate is a stabilizer to prevent gelling,"Fascat" 4020 is a disbutyl tin dilaurate curing catalyst, and"Solvesso" 100 is an aromatic solvent. The clearcoat composition issprayed at a viscosity of 35"Fisher #2 cup. It is sprayed over clearcoatwet on wet at 1.8-2.0 mil thickness and baked 30 min. at 265° F. Theclearcoat typically exhibits an out of oven hardness of 3-4 Knoop, agloss of 85-95 at 20° and a DOI of 80-90. The clearcoat had excellentdurability and crack resistance.

Various modifications, alterations, additions, or substitutions of thecomponents of the composition and process of this invention will beapparent to those skilled in the art without departing from the scopeand spirit of this invention and it should be understood that thisinvention is not unduly limited to the illustrative embodiments setforth herein.

What is claimed is:
 1. A composition useful for coating a substrate,which composition comprises:(a) from about 20 to 90% by weight, based onthe weight of binder solids, of a film-forming alkoxysilane-functionalpolymer having a weight average molecular weight of about 500-30,000comprising from about 30 to 95% by weight, based on the weight of thealkoxysilane-functional polymer, of ethylenically unsaturated monomerswhich do not contain an alkoxysilane functionality and about 5 to 70% byweight ethylenically unsaturated monomers which contain an alkoxysilanefunctionality; and (b) from about 10 to 60%, based on the weight of thebinder solids, of a non-aqueous dispersed polymer having an averageparticle size of at least about 0.1 microns, comprising:(i) amacromolecular core; and (ii) a plurality of essentially epoxy freemacromonomer chains, attached to the macromolecular core, having aweight average molecular weight of about 1,000 to 30,0000, comprising 5to 30% by weight, based on the weight of macromonomer, of polymerizedethylenically unsaturated monomers which comprise a hydroxyfunctionality capable of crosslinking with alkoxysilane functionalitiesin said alkoxysilane-functional polymer; and about 70 to 95% by weight,based on the weight of the macromonomer, of at least one otherpolymerized ethylenically unsaturated monomer without a hydroxyfunctionality; and (c) from about 25 to 50% by weight, based on theweight of the composition, of a liquid organic carrier.
 2. The coatingcomposition of claim 1, wherein the film-forming alkoxysilane-functionalpolymer may also comprise hydroxy functional groups.
 3. The coatingcomposition of claim 1, further comprising a polyol polymer having ahydroxyl number of about 50-200 and a weight average molecular weight ofabout 1,000-200,000.
 4. The coating composition of claim 3, wherein thepolyol polymer comprises an acrylic polyol.
 5. The coating compositionof claim 1 further comprising a crosslinking agent.
 6. The coatingcomposition of claim 5, wherein the ratio of the alkoxysilane-functionalpolymer to the dispersed polymer is 5:1 to 1:1.
 7. The coatingcomposition of claim 5, wherein the crosslinking agent is an alkylatedmelamine formaldehyde.
 8. The coating composition of claim 1, whereinthe the film-forming polymer is an acrylosilane polymer.
 9. The coatingcomposition of claim 3, wherein the ethylenically unsaturated monomerswhich contain a alkoxysilane functionality have the following structuralformula: ##STR4## wherein R is selected from the group consisting ofCH₃, CH₃ CH₂, CH₃ O, and CH₃ CH₂ O; R₁ and R₂ are individually selectedfrom the group consisting of CH₃ and CH₃ CH₂ ; and R₃ is selected fromthe group consisting of H, CH₃, and CH₃ CH₂ and n is O or a positiveinteger of not greater than
 8. 10. The coating composition of claim 3,wherein the ethylenically unsaturated monomers which contain a silanefunctionality have the following structural formula: ##STR5## wherein Ris selected from the group consisting of CH₃, CH₃ CH₂, CH₃ O, and CH₃CH₂ O; R₁ and R₂ are individually selected from the group consisting ofCH₃ and CH₃ CH₂ ; and n is O or a positive integer of 1-10.
 11. Thecoating composition of claim 3 wherein the ethylenically unsaturatedmonomers which contain a silane functionality have the followingstructural formula: ##STR6## wherein R is selected from the groupconsisting of CH₃, CH₃ CH₂, CH₃ O, and CH₃ CH₂ O; R₁ and R₂ areindividually selected from the group consisting of CH₃ and CH₃ CH₂ ; andR₄ is selected from the group consisting of H and CH₃, R₅ is an alkylenegroup having 1-5 carbon atoms and n is positive integer of 1-8.
 12. Thecoating composition of claim 8, wherein the acrylosilane comprisespolymerized monomers of about 15-25% by weight styrene, about 25-50% byweight trimethylcyclohexyl methacrylate or isobutyl methacrylate, andabout 30-60% by weight of a silane-containing monomer.
 13. The coatingcomposition of claim 12, wherein the alkoxysilane monomer ismethacryloxypropyltrimethoxy silane.
 14. The coating composition ofclaim 1, whereina. The core of the dispersed polymer comprisespolymerized monomers of styrene, an alkyl methacrylate, where the alkylhas 1-6 carbon atoms, an ethylenically unsaturated monocarboxylic acid;and b. The macromonomers attached to the core comprise polymerized alkylmethacrylate, alkyl acrylate monomers, or mixtures thereof, each having1-12 carbon atoms in the alkyl group, hydroxy alkyl acrylate or hydroxyalkyl methacrylate monomers or mixtures thereof, each having 1-4 carbonatoms in the alkyl group and glycidyl acrylate or glycidyl methacrylate.15. The coating composition of claim 1, wherein the composition containsabout 0.1-4% by weight, based on the weight of the composition, of anacid catalyst.
 16. The coating composition of claim 1, wherein thecomposition contains about 0.1-5% by weight, based on the weight of thecomposition, of an organo tin catalyst, an aluminum catalyst or azirconium catalyst.
 17. A process for coating a substrate, comprisingthe steps of:a. applying a layer of a pigmented basecoating to thesubstrate to form a basecoat thereon; b. applying to the basecoat alayer of the composition of claim 1 to form a top coat over saidbasecoat; c. curing the basecoat and topcoat to form a basecoat andtopcoat on the substrate.
 18. A substrate coated with a compositionclaim
 1. 19. A substrate coated with a pigmented basecoat of a filmforming polymer and a pigment, and a clearcoat comprising thecomposition of claim 1 in superimposed adherence to the basecoat. 20.The composition of claim 1, wherein the non-aqueous dispersed polymercomprises 50-90%, by weight of the dispersed polymer, of saidmacromolecular core, and 10-50%, by weight of the dispersed polymer, ofsaid macromonomer chains.
 21. The composition of claim 1, wherein themacromolecular core has an average particle size of 0.1 to 0.5 microns.22. The composition of claim 1, wherein the composition is a one-packagesystem and comprises an effective amount of a water scavenger.
 23. Thecomposition of claim 22, wherein the water scavenger is trimethylorthoformate or triethyl orthoformate.